German Versions of the Nightmare Effects Survey (NES) and the Nightmare Frequency Questionnaire (NFQ): Psychometric Properties in a Sample of Adult Chronic Nightmare Sufferers

The Nightmare Effects Survey (NES) and the Nightmare Frequency Questionnaire (NFQ), 2 widely used questionnaires in nightmare research, were translated into German and tested in a sample of 86 adult chronic nightmare sufferers. Participants completed the questionnaires together with measures of nightmare-and sleep-related factors and psychopathology and kept a nightmare diary for 3 weeks. Psychometric properties were determined: The German NES showed high internal consistency (Cronbach's alpha = .898) and split-half reliability (r = .889) and a unifactorial structure (46.33% variance explained). The German NFQ and the prospective nightmare diary yielded similar frequencies for nights with nightmares, a significantly higher value for number of nightmares in the diary, and correlations of .621 and .570 between measures of nights with nightmares and number of nightmares, respectively. The 2 scores of the German NFQ were highly intercorrelated (r = .838). Correlations with related constructs were insignificant or low for the German NFQ (between r = .09 and r = .28) and medium for the German NES (between r = .27 and r = .59). The German NFQ and NES proved to be reliable, useful, and efficient to quantify nightmares and their effects. The findings demonstrate the questionnaires' construct validity and support theories that differentiate between nightmare frequency, nightmare effects, and nightmare distress. German translations are provided as supplemental material.